Werewolves, vampires, and other supernatural beings have become a staple in current genre fiction. One problem I've seen in many of the fight scenes involving these creatures is created by a flaw in worldbuilding.
Consider this scene from a contemporary novel. The vampire protagonist is in a dangerous part of a major city, and he's attacked by a large pack of demon-possessed humans. He fights them off until some of his vampire friends arrive, and all the demon-possessed humans are murdered. Fortunately, no normal humans saw the fight so the vampires' existence remains a secret. They stalk away into the night.
What's the problem? Simple. How can a race remain a secret for long with widespread killings and the sheer number of combatants on both sides? Wouldn't the police become a tad suspicious if the murders kept building up? Wouldn't a medical examiner suggest that someone with superhuman strength ripped these guys apart? And what about that weird DNA found on the ripped throat of one of the victims?
The fight itself can be perfectly choreographed and written, but at its end, when all the bodies are lying there, and the vampires are leaving the scene, some readers will go, "Wait a minute. What about the police? What about...." If you leave that kind of question, the fight scene has failed.
In a recent urban fantasy novel, the human-shaped demons spent the novel taking human prey while the vampires were killing the demons and the vampire hunters were killing the vampires, yet the humans and the police were apparently totally clueless about the existence of any of these creatures and unconcerned at a body count that fit a war zone, not an American city.
For a race like vampires or werewolves to remain secret, they must have very small numbers because a large number of anything can't be kept secret, or the race rarely makes contact with humans.
If they take prey, they must dispose of the bodies so no evidence of the deaths will ever be found. Their prey must also be on the edges of human society so that their loss won't be obvious. In other words, vampires should attack a homeless person, not the beautiful young countess surrounded by friends, retainers, and family.
Vampires definitely shouldn't attack tourists in a town which supports itself with tourism. Considering the incredible national coverage and outrage caused by just a few tourist deaths in places like Miami and New Orleans in recent years, it's highly unlikely that dozens of tourists becoming monster chow wouldn't cause a similar outcry and intense scrutiny.
Real world logic applies even to supernatural characters. Make the fight and its outcome logical, or you've failed.
